Connected: An Internet Encyclopedia
RFC 821 - APPENDIX B: NCP Transport service

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### APPENDIX B: NCP Transport service

The ARPANET Host-to-Host Protocol [4] (implemented by the Network Control Program) may be used in the ARPANET.

Connection Establishment

  The SMTP transmission channel is established via NCP between the sender process socket U and receiver process socket L. The Initial Connection Protocol [5] is followed resulting in a pair of simplex connections. This pair of connections is used as the transmission channel. This protocol is assigned the contact socket 25 (31 octal), that is L=25.

Data Transfer

  The NCP data connections are established in 8-bit byte mode. The SMTP data is 7-bit ASCII characters. Each character is transmitted as an 8-bit byte with the high-order bit cleared to zero.

Next: APPENDIX C: NITS

Connected: An Internet Encyclopedia
RFC 821 - APPENDIX B: NCP Transport service